Fuel injectors typically comprise an electromagnetically actuated needle valve disposed in a fuel volume and which needle valve is reciprocated axially within the fuel volume in response to energization and deenergization of an actuator to selectively open and close a flow path through the fuel injector. Particularly, the valve body or housing defining the fuel volume has an aperture or orifice at one end about which is formed a seat for the end of the needle valve whereby reciprocating motion of the needle valve enables an intermittent flow of fuel through the orifice. Fuel emitted from a fuel injector is typically atomized downstream of the orifice to provide the necessary fuel/air mixture in the combustion chamber of the engine.
In a companion application by the present inventors U.S. Ser. No. 08/686,959 filed Jul. 26, 1996 and entitled Fuel Injector With Air Bubble/Fuel Dispersion Prior to Injection and Methods of Operation, there is provided a fuel injector in which an air bubble/fuel dispersion is provided within the fuel volume of a fuel injector upstream of the injector orifice. This is accomplished by supplying air under pressure through one or more porous members situate in an air inlet in communication with the fuel volume upstream of the orifice. The air flows through the porous member and forms bubbles of a predetermined size in the fuel within the fuel volume. The bubbles are sized by the pore size of the porous member such that the air bubbles dispersed in the fuel in the fuel volume do not substantially rise. Consequently, a predetermined mass of a two-phase air bubble/fuel dispersion can be ejected through the orifice of the fuel injector for improved atomization, fuel economy and burn with resulting lower emissions. The present invention provides novel and improved apparatus and methods for supplying fuel and air to a fuel injector of that type and over a predetermined time interval.